In the production of lubricating oils solvent extraction processes are employed to separate the aromatic fraction from the more desirable paraffinic fraction. In such processes a solvent which preferentially dissolves aromatic hydrocarbons and which is at least partially immiscible with the charge oil under the conditions of contacting is employed. A suitable solvent is furfural.
After contacting the charge oil with furfural under conventional solvent refining conditions, the resulting furfuralaromatic fraction is then fractionally distilled to separate the furfural which is then recycled to the solvent extraction zone. The aromatic fraction, commonly referred to as an aromatic extract, can be employed in the manufacture of ink oils. Before such aromatic extract can be effectively employed in the ink oils, the concentration of the furfural must be reduced to less than 50 parts per million (ppm). The most efficient of the distillation processes employed in the separation of furfural from the aromatic extract produces an aromatic extract product normally containing greater than 100 ppm furfural.